A former U.S. Marine pilot fighting extradition from Australia on U.S. charges of training Chinese military pilots to land on aircraft carriers, unknowingly worked with a Chinese hacker, his lawyer said.

Daniel Duggan, 55, a naturalised Australian citizen, feared requests by Western intelligence agencies for sensitive information were putting his family at risk, the lawyer said in a legal filing seen by Reuters.

The lawyer's filing supports Reuters reporting linking Duggan to convicted Chinese defence hacker Su Bin.

Duggan denies the allegations that he broke U.S. arms control laws. He has been in an Australian maximum security prison since his 2022 arrest after returning from six years working in Beijing.

U.S. authorities found correspondence with Duggan on electronic devices seized from Su Bin, Duggan's lawyer Bernard Collaery said in the March submission to Australian Attorney General Mark Dreyfus, who will decide whether to surrender Duggan to the U.S. after a magistrate hears Duggan's extradition case.

The case will be heard in a Sydney court this month, two years after his arrest in rural Australia at a time when Britain was warning its former military pilots not to work for China.

Su Bin, arrested in Canada in 2014, pleaded guilty in 2016 to theft of U.S. military aircraft designs by hacking major U.S. defence contractors. He is listed among seven co-conspirators with Duggan in the extradition request.

Duggan knew Su Bin as an employment broker for Chinese state aviation company AVIC, lawyer Collaery wrote, and the hacking case was "totally unrelated to our client".

Although Su Bin "may have had improper connection to (Chinese) agents this was unknown to our client", Duggan's lawyer wrote.

AVIC was blacklisted by the U.S. last year as a Chinese military-linked company.

Messages retrieved from Su Bin's electronic devices show he paid for Duggan's travel from Australia to Beijing in May 2012, according to extradition documents lodged by the United States with the Australian court.

Duggan asked Su Bin to help source Chinese aircraft parts for his Top Gun tourist flight business in Australia, Collaery wrote.

The Australian Security Intelligence Organisation (ASIO) and U.S. Navy criminal investigators knew Duggan was training pilots for AVIC and met him in Australia's Tasmania state in December 2012 and February 2013, his lawyer wrote.

ASIO and the U.S. Navy Criminal Investigation Service did not respond to Reuters requests for comment on the meetings. ASIO has previously said it would not comment as the matter was before the court.

"An ASIO officer suggested that while carrying on his legitimate business operations in China, Mr Duggan may be able to gather sensitive information," his lawyer wrote.

Duggan moved to China in 2013 and was barred from leaving the country in 2014, his lawyer said. Duggan's LinkedIn profile and aviation sources who knew him said he was working in China as an aviation consultant in 2013 and 2014.

He renounced his U.S. citizenship in 2016 at the U.S. embassy in Beijing, backdated to 2012 on a certificate, after "overt intelligence contact by U.S. authorities that may have compromised his family safety", his lawyer wrote.

His lawyers oppose extradition, arguing there is no evidence the Chinese pilots he trained were military and that he became an Australian citizen in January 2012, before the alleged offences.

The United States government has argued Duggan did not lose his U.S. citizenship until 2016.

(Reuters)

Former U.S. Marines Corp pilot Daniel Duggan, who is facing extradition to the United States for allegedly breaking U.S. arms control law after he trained Chinese pilots, poses for a picture in this undated handout picture. (Reuters)

US Marine pilot arrested in Australia worked with Chinese hacker, lawyer says